Fertilization And Early Pregnancy Reproductive Physiology Practice Quiz

LH stimulates the granulosa cells to secrete progesterone. Progesterone is a hormone that plays a crucial role in the menstrual cycle and is essential for ovulation. It helps prepare the uterus for potential implantation of a fertilized egg. Therefore, the acquisition of the LH receptor by the granulosa cells is necessary for the production and secretion of progesterone, which is required for ovulation of the dominant follicle.

All of these events are associated with changes in intracellular calcium, and in
some instances (such as GVBD) the changes in calcium are classic hallmark indicators of the event.
In some events, such as hyperactivation and the acrosome reaction, because changes in intracellular occur so rapidly it has been difficult for scientists to determine if the changes in calcium directly cause the event or are a direct result of the event. Regardless, changes in calcium are associated with the events occurring.

Thinning of the cervical mucous, coupled with increased vaginal secretions
during intercourse, enhance sperm transport through the lower portion of the female reproductive tract. Slight contractility of the uterus aids in sperm transport through the endometrial lumen. Cilia beat frequency becomes rhythmical and secretions increase in the fallopian tube, which enhances both sperm and oocyte transport. Decreased vaginal secretions, increased uterine blood flow, decidualization of the endometrial stroma and decreased uterine contractility are all effects induced by progesterone during the secretory phase of the menstrual cycle, and are not associated with ovulation.

This woman may be experiencing peri‐menopause, but nausea is not a typical
symptom associated with menopause. The history of no menstrual period for 3 months and onset of nausea is
indicative of pregnancy, likely the end of the first trimester. An hCG test will quickly determine pregnancy status. The
woman is worried about menopause, but as a physician you need to look at the entire picture. Additionally, you are
told in the first sentence that the woman is in a "monogamous relationship", therefore in this instance you should
assume the woman is engaged in sexual activity.
Estrone is considered the estrogen of menopause, but in this case, it would be prudent to evaluate progesterone and
estradiol levels to first determine cyclicity. If estradiol levels are normal, then the woman may have an underlying
pathophysiological disorder, such as PCOS or leiomyoma (uterine fibroids). Reproductive pathophysiological disorders
will be covered in detail in Semester 4.

You recognized that LH and hCG exhibit a high degree of homology and both
bind with high affinity to the LH receptor. In a typical menstrual cycle, the peak of the LH surge occurs approximately
10‐12 hours before ovulation, which is considered the same day as ovulation (i.e. within a 24 hr period). An acute
release of hCG would mimic the LH surge, resulting in ovulation of the dominant follicle.
You also remembered that the corpus luteum has a finite lifespan of 12‐16 days, and therefore to induce a 28 to 30 day
menstrual cycle, ovulation must occur approximately 12‐16 days before menses. Thus, of the choices offered the
optimal day to induce ovulation is Day 15, since this will result in elevated progesterone for approximately 12‐16 days
resulting in a menstrual cycle length of 27‐31 days.
Day 18 is the next best choice, but taking the hCG pill on Day 18 would likely result in an extended menstrual cycle
lasting 30‐34 days.

Blocking the GnRH receptor will result in decreased production of LH and FSH,
which will subsequently inhibit growth of the dominant follicle. Interestingly, you could also suppress follicle growth and development by administering receptor antagonists designed to inhibit FSH receptor pathway or the LH receptor pathway, but the best answer is a GnRH antagonist that blocks both
LH and FSH activity. Recall the 2‐cell theory of steroidogenesis, and how LH and FSH action on the theca and granulosa cells is a complementary system that results in estradiol production.

An adequate functionalis layer is required to support an invading blastocyst
during the process of implantation. Progesterone exerts profound effects on the functionalis layer, inducing sacculation
of the endometrial glands and stimulating epithelial secretion.
An underdeveloped endometrium is not capable of supporting implantation, but to date there is no evidence to suggest an inadequate functionalis zone will inhibit gamete transport or subsequent fertilization. The processes of decidualization and menstruation will occur in a normal manner, there will just be less tissue to undergo differentation and enzymatic breakdown during those processes, respectively.

Granulosa‐lutein cells (GLC) and theca‐lutein cells (TLC) both express
functional LH receptors, and the GLC secrete progesterone and estrogen whereas the TLC secrete androgen
(predominantly androstenedione) and progesterone. The GLC then aromatize the androgen into estrogen. These cells
types can also be distinguished histologically, since the TLC express high levels of CYP17 (the enzyme required to convert
progesterone into androgen) whereas the GLC express CYP19 (aromatase, required to convert androgen into estrogen).
Remember that the primary function of the CL is to secrete progesterone.
Steroidogenesis Summary:
Granulosa cells = estrogen during the follicular phase
Granulosa cells = estrogens and progesterone during the ovulatory window (after they acquire the LH
receptor)
Granulosa-lutein cells = progesterone and estrogen during the luteal phase
Theca cells = androgens
Theca-lutein cells = androgens and subsidiary amounts of progesterone
hCG = binds to the LH receptor and therefore maintains luteal steroidogenesis resulting in continued
progesterone production
The CL predominantly secretes progesterone. Follicles predominantly secrete estrogen.

A rise is progesteone is always associated with ovulation and formation of a functional corpus luteum, but progesterone levels actually start to increase prior to ovulation, and these levels then climb rapidly following ovulation and formation of the corpus luteum. Cohorts of granulosa cells express a functional LH receptor prior to ovulation, and during the peri‐ovulatory period these cohorts of granulosa cells bind LH and actively start secreting progesterone into the maternal circulation. Thus, this early rise in progesterone appears to be an essential component of the physiological processes regulating ovulation.
Following a successful ovulation, the follicle will involute and form the corpus luteum. The luteinized granulosa cells will then produce large quantities of progesterone, the hormone of pregnancy that is required to prime the uterus for subsequent implantation. Day 15 or 16 would be reasonable answers if the question had asked for changes in measurable serum levels of progesterone. These changes in progesterone prior to ovulation, especially as measured in a single blood draw, may be below the threshold of assay detection in a single serum sample. Measurable increases in serum progesterone, secreted by the newly formed corpus luteum, are detectable (above baseline) within 24 ‐ 48 hrs following ovulation, (and most of the time much sooner, within 6 ‐12 hrs). Further, increases in progesterone above baseline are always indicative of a successful ovulation and associated with the formation of a corpus luteum.

It is estimated that 80% of all zygotes are lost to spontaneous abortion before
implantation, and that another 20‐30% of all pregnancies are lost during the implantation process. Thus, the slightly
extended menstrual cycle is most likely due to a spontaneous abortion during very early pregnancy.
The only other logical answer is an extended proliferative phase, which is the primary cause for variations in the
menstrual cycle (remember the secretory/luteal phase is 12‐16 days and dependent on the lifespan of the CL). However,
because this woman experienced 10/11 menstrual cycles of exactly 29 days (3 prior to trying to get pregnant and 7/8
while trying), this suggests her proliferative phase is tightly controlled. This woman was having unprotected intercourse
for 8 months, and therefore the lone deviation in menstrual cycle length in this woman's specific situation is more likely
due to a spontaneous abortion than a result of an extended proliferative phase.

All three estrogens are secreted in large amounts and (estrone, estradiol,
estriol) act as vasodilators to increase blood flow to the uterus and growing placenta. Estriol is synthesized by the fully functional placenta after the luteal‐placental steroidogenic shift, and is considered the estrogen of pregnancy. Additional roles of estrogen during pregnancy are being examined, but to date, remain largely unknown.

Mature sperm survive in the epididymis for approximately 4 to 6 weeks before
being ejaculated or being catabolized and resorbed. A man is informed that he can father a child for up to 6 weeks
following a vasectomy. Most urologists and or vasectomy clinics will test a man's sperm count after 20 ejaculations or 6
weeks following a vasectomy.
Sperm are able to survive for this extended duration due to the lower temperatures within the scrotum. In the female
reproductive tract, most sperm die within 24‐48 after ejaculation, although viable sperm can be recovered up to 5 days
after a single ejaculation during intercourse.

A fully functional placenta begins to secrete increasing concentrations of estriol
at approximately 8 weeks of pregnancy. The rise in estriol indicates that the maternal‐fetal‐placental unit is fully functional. Therefore, the rise in estriol is associated with the luteal‐placental shift, which typically occurs between 7‐9 weeks of gestation. The other four major events occur within the first 2 weeks of pregnancy and are not associated with estriol.